This invention relates to processes in the art of chemistry which concentrate and remove organic pesticide residues which are suspended or dissolved in spent aqueous treatment solutions for agricultural products, and to apparatus designed for carrying out said processes. After harvesting, fruits and vegetables are treated with various pesticide chemicals in solution to control various diseases caused by plant pathogens (both bacterial and fungal). Such treatments permit longer term storage and are normally applied by drenching or dipping. These pesticide containing solutions are normally aqueous and after use in treatment are considered hazardous waste with the attendant problems both economic and practical for their disposal. The problems are exacerbated by the high volumes of the solutions and the dilute concentrations of the pesticides contained in them.
It has been found that for waste water comprising spent aqueous solutions from apple treatment containing the anti scald agents diphenylamine or 6 ethoxy-1,2-dihydro-2,2,4-trimethyl quinoline (ethoxyquin) along with other dissolved and suspended organic matter, use of particular flocculating agents followed by separation of the supernatant liquid from the flocculated material and subsequent treatment of the supernatant liquid with activated charcoal results in a significant removal of the diphenylamine or ethoxyquin from the liquid together with a significant reduction of much of the other organic materials.